High Thermal Conductivity Polymer Composites PI: Asegun Henry, Ph.D. Co-PI: Kyriaki Kalaitzidou, Ph.D. Graduate Students: Wei Lv, Sanzida Sultana Intel Update Meeting: 7/11/2014

Objective and Approach Objective – Higher TC chassis Polymer chain alignment in fibers High thermal conductivity fillers Approach – Experiments + Modeling Sintered fibers High TC matrix Mechanical Incorporate fillers Measure composite TC Use modeling to understand experiments Use modeling to evaluate alternatives AH

Overview of Experimental Approach Melt spinning of fiber Step 1 Zylon Fiber stretching modulus measurement Spectra High thermal conductivity composite Sinter fibers and xGnP layers Single fiber coating Thermoset (Epoxy) Thermoplastic (PP) xGnP Film (lab) Step 2 XG leaf (commercial) AH Fiber winding automation Guide and tension application for better fiber alignment Step 3 Scale up

Sintering of Zylon Polybenzobisoxazole (PBO) KK Not sure what cahill is Thermal conductivity of high modulus polymer fibers 1 Thermoset – no melting point Doesn’t sinter Attainable highest temperature is 343o C while decomposition temperature of zylon is 650 o C . Sintering attempt of zylon fiber 1. Wang, X, Ho, V., Segalman, R. A., Cahill, D. G. dx.doi.org/10.1021/ma400612y | Macromolecules 2013, 46, 4937−4943.

Graphite Film Fabrication Epoxy (low viscosity, casting) 20% loading  agglomeration PP (compression molding) PP film coating  agglomeration Move to xG leaf xGnP having thermal conductivity of 1500-3000 W/mK KK Discontinuous deposition of 1 μm xGnP on PP film

Graphite Films xGnP film XG leaf Price: $500 /kg 50 µm thickness 11 inch 1.69 inch Move to slide 6 Price: $500 /kg 50 µm thickness Tensile strength 10 MPa Thermal conductivity In-plane: 500 W/mK Through: 3 W/mK Price: $199/kg 140 µm thickness Thermal conductivity2 In-plane: 178±12 W/mk Through: 1.28±0.12 W/mk 2.Thermal conductivity of exfoliated graphite nano-platelet paper, Jinglei Xiang, Lawrence T. Drzal, Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI 48824-1226, USA

Spectra Fiber Sintering Fiber Characteristics: Modulus: 70±18 GPa (based on DMA) 113 GPa (based on MSDS) Melting point: 147 o C Sintering Conditions: 115 o C, 250, 350 psi, varied sintering time with thickness 40 layer & 5 layer sample 50 μm Sintered fiber (5 layer) on flat Aluminum mandrel 50 μm KK 1 cm incised sample (40 layer) for graphene layer insertion SEM micrograph of 5 layer sample cross-section 7

Samples for TC Measurement Types of Sample: Spectra 2% xGnP/Spectra 7% xGnP/Spectra 21% xGnP/Spectra Dimensions: 5.4cm X 2.9 cm X 4.3 mm Surface Roughness: 0.365 µm Top KK Bottom

Sample Architecture Z direction : fibers are aligned, in-plane direction of graphite layer Y direction : transverse to fiber layers and graphite layer X direction : Transverse to fiber alignment, another in-plane direction of graphite layer. kz > kx > ky Move to slide 9 Y Z X 3D view of sample

Sintering Effects Sintering condition Melting Peak, Tm oC Crystallization Peak, Tcr oC Melting Enthalpy, J/g Crystallinity, % 0 hour 149 119 210±16 71±5 3 hours 220±9 75±3 6 hours 231±8 80±1 9 hours 236±10 80±3 Sintering  No significant effect on crystallinity KK Crsytallinity calculated using the enthalpy of fusion of HDPE with 100% Crystallinity as 293.6 J/g 3. 3. Wunderlich, B. Thermal Analysis. Academic Press: San Diego, 1990. *Results based on 3 data points.

Scaled Up Fabrication Setup Fiber winded on the mandrel Mandrel motor Motor for linear motion Actuator for graphite layer tensioner Guide Mandrel AH Linear actuator tensioner Fiber spool

Procedure Feed the fiber and tie one end on the mandrel Manual rotation of mandrel Adjust Tensioner Pause & Add Graphite Layer Wind Fibers N cycles to build thickness Cut the sample from mandrel Sinter the sample in hot press AH Sinter to adhere edges Measure thermal conductivity (1D Fin)

Speed of Different Components Graphite Deposition 10-30 min intervals Rotational motion: 400 rpm AH Linear motion 0.55 rpm Every 2 min

Cost Analysis Description Quantity Unit price Teknic stepper motor ( mandrel ) 2 $324 Raptor RTX Gearbox 1 $675 Linear actuator $838 Teknic stepper motor (linear motion) Power supply $199 Controller $1079 Total $3439 AH

Cost Analysis Description Quantity Unit price 8718M_mandrel motor 1 $220 R1025 $401 Controller $200 4118S-04S motor $55 R256 controller $215 Linear system $950 Total $2041 AH

Timeline Tasks Component ordering Thermal conductivity measurements 07/14 08/14 09/14 10/14 11/14 12/14 01/15 02/15 03/15 04/15 05/15 Component ordering   Thermal conductivity measurements Scale-up assembly Automation tests Winding tests Composites manufacture Refinement of the process Fit model to experiments Predictions of alternative materials